Pyrido-indole derivatives

ABSTRACT

Pyrido(2,3-b)indoles having depressant activity on the C.N.S. are prepared by cyclization of 2-aminoindole-3-propionic acid derivatives. The compounds have the following general formula:   WHEREIN THE DOTTED LINES REPRESENT AN ADDITIONAL BOND LOCALIZED IN ONE OF THE TWO POSSIBLE POSITIONS; R represents lower alkyl of 1 to 4 carbon atoms, and benzyl; R1 represents hydrogen, lower alkyl of 1 to 4 carbon atoms, benzyl, lower aliphatic acyl of 1 to 4 carbon atoms; R2 represents hydrogen, lower alkyl of 1 to 4 carbon atoms and benzyl; AND R1 and R2 may not be present simultaneously.

United States Patent [191 Winters et al.

[ PYRlDO-[NDOLE DERIVATIVES [75] Inventors: Giorgio Winters; Nunzio Di Mola,

both of Milan, Italy [73] Assignee: Gruppo Lepetit S.p.A., Milan, Italy [22] Filed: Sept. 3, 1974 [211 App]. No.: 503,026

[30] Foreign Application Priority Data Sept. 10, 1973 United Kingdom 42368]?! [52] US. Cl. 260/297 1''; 424/263 [51] Int. Cl! C07D 209/56 [58] Field of Search 260/296 T, 296 A [56] References Cited FOREIGN PATENTS OR APPLICATIONS 39-20857 9/1964 Japan 260/296 A 39-22979 l0/l964 .lapan.... 260/296 A 4l-27l3 2/1966 .Iapan.... 260/296 A 41-2790 2/l966 Japan.... 260/296 A 4l-279l 2/l966 Japan 260/296 A $47,985 6/l930 Germany 260/296 T OTHER PUBLICATIONS Chemical Abstracts, Vol. 53, Cols. 424-426, (1959), (Abst. of Sugasawa et al.).

Chemical Abstracts, Vol. 63, Cols. 18058 to 18059 (1965), (Abst. of Yamada et all).

Chemical Abstracts, Vol. 74, Abst. No. 54063u, (i971). (Aim. of Grandberg et al.).

Chemical Abstracts. Vol. 76, Abst, 153,639j, (i972), (Abst. of Borisov et al.).

[ Dec. 23, 1975 Primary Examiner-John D. Randolph Attorney, Agent, or Firm-Theodore Post; C. Kenneth Bjorh [57] ABSTRACT Pyrido[2,3-b]indoles having depressant activity on the CNS. are prepared by cyclization of Z-aminoindole- 3-propionic acid derivatives. The compounds have the following general fonnula:

6 Claims, No Drawings PYRlDO-INDOLE DERIVATIVES SUMMARY OF THE INVENTION This invention relates to new pharmacologically active pyrido[2,3-b] indole derivatives. The new compounds have the following general formula wherein the dotted lines represent an additional bond localized in one of the two possible positions;

R represents lower alkyl of l to 4 carbon atoms and benzyl;

R, represents hydrogen, lower alkyl of l to 4 carbon atoms, benzyl and lower aliphatic acyl of l to 4 carbon atoms and it is present only if the symbol R is absent and the double bond is located between the carbon atoms in position 2 and 3 of the indole ring.

R represents hydrogen, lower alkyl of l to 4 carbon atoms and benzyl and it is present only if the symbol R, is absent and the double bond is located between the positions 1 and 2 of the pyridine ring.

In the specification and in the claims the term lower alkyl of l to 4 caron atoms designates an aliphatic radical such as methyl ethyl, propyl, butyl, isopropyl, isobutyl and tert-butyl. The term lower aliphatic acyl of l to 4 carbon atoms designates an alcanoyl radical such as formyl, acetyl, propionyl, butyryl and isobutyryl.

When in the structure formula I either R, or R is hydrogen the terms herein represented actually corresponds to two tautomeric forms of the same compound.

The new compounds are endowed with useful pharmacological properties and in particular they are active as depressants of the central nervous system. Their toxicity is very low.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process for preparing the compounds of the invention consists in the cyclization of suitable indole derivatives of the general formula bond is located between the carbon atoms in position 2 and 3 of the indole ring;

R has the same meaning as before and it is present only if the symbol R, is absent and the double bond is located between the iminic substituent and the carbon atom in the position 2 of the indole ring.

R represents hydrogen and lower alkyl of 1 to 4 carbon atoms.

The cyclization runs through the following scheme and is carried out in an organic solvent selected from organic polar solvents such as for instance lower alkanols, ethylene glycol lower alkyl ethers, dimethylformamide and dioxane in the presence of a basic agent such as an alkali metal acetate or carbonate, an alkali metal amide or lower alkoxide.

According to a convenient procedure, the indole derivative, preferably as the hydrohalide, is mixed with about 2-2.5 equimoleeular proportions of the basic agent in the selected solvent. The mixture is then heated at a temperature varying from 60 to C for a period of time which may vary from a few minutes to 6-8 hours. The solvent is then concentrated and diluted with water. The solid precipitated may be purified by crystallization from common organic solvents such as lower alkanols or tetrahydrofuran.

When in the compound obtained according to the above reaction scheme either R, or R represents hydrogen, simple reaction procedures may lead to substitution of the hydrogen atom with lower alkyl of 1 to 4 carbon atoms, benzyl or lower aliphatic acyl group of 1 to 4 carbon atoms. More particularly, reaction with lower alkyl halogenides in dimethylformamide in the presence of sodium hydride or with acylating agents such as acid anhydrides and halogenides leads to alkylation or acylation of the nitrogen atom of the pyridine ring. Reaction with benzyl bromide in dimethylformamide in the presence of sodium hydride gives a mixture of the two possible isomers of formula I where R, or R, is benzyl. These latter compounds may be separated by chemical methods.

The compounds of the invention are crystalline solids and are fairly soluble in acetone, chloroform and dioxane, sparingly soluble in lower alkanols and hardly soluble in water.

The starting indole derivatives ll are prepared substantially according to the process described by A. N. Kost et al. in Dokl. Akad.Nault.U.S.S.R. 200 (2), 342, 1971 (CA. 76, 34047e) which involves heating l-phenyI-Z-acylhydrazine of the formula lll wherein R and R have the same meaning as before, R, and R each independently represents hydrogen, lower alkyl or benzyl with the proviso that at least one represents hydrogen, in the presence of a condensing agent such as POCI or PCl The pharmacological properties of the invention compounds were investigated in the pole climbing avoidance test according to the method of L. Cook et a1. Ann.N.Y. Acad.Sci. 66, 740, 1957 modified by C. Maffii (J.Pharm.Pharmacol., ll, 129, 1959). This test is related to anxiolytic and tranquillizing effects.

In a representative experiment on conditioned rats the compound 9-methyl-3,4-dihydro-pyrido[2,3-b] indole-2(lH)-one at a dose level of mg/Kg i.p. in 8 out of ten rats showed inhibition of the secondary conditioned response without affecting the unconditioned response and the primary conditioned response. The LD values are 700 mg/Kg i.p. and 1000 rng/Kg p.o. in mice. In a similar experiment with the compound l,9- dimethyl-3 ,4-dihydro-pyrido[2,3-b]indole-2( lH)-one all ten rats tested showed inhibition of the secondary conditioned response at a dose level of 30 mg/kg. i.p. The LD value is higher than I000 mg/kg'po. Accordingly the present invention provides a therapeutic composition comprising as the active ingredient a compound of the invention together with a pharmaceutically acceptable carrier.

The following examples illustrate the invention without limiting its scope.

EXAMPLE I 9-Methyl-3 ,4-dihydro-pyrido[ 2,3-b]indole-2( l H )-one 54.5 Grams of lmethyl=3-(2-carbomethoxyethyl)-2- iminoindoline hydrochloride (m.p. 206C) and 41.5 g. of anhydrous sodium acetate in 1000 ml. of ethanol are refluxed for 5 hours and then the hot reaction mixture is filtered; after concentration to about 300 ml., 500 ml. of ice water are added to the filtrate. The product precipitated is crystallized from acetone. Yield 27 g. M.p. 23742C.

EXAMPLE 2 9-Benzyl-3 ,4-dihydro-pyrido[2,3-b] indole-2( l H )-one 4l .5 Grams of l-benzyl-3-(2-carbomethoxyethyl)-2- iminoindoline hydrochloride (m.p. 226-8C) and 32 g. of anhydrous sodium acetate are refluxed for 6 hours in 800 ml. of ethanol. The hot reaction mixture is then filtered and the filtrate is concentrated to a small volume. Addition of 500 ml. of water gives a precipitate which is purified by crystallization from ethanol. Yield 23.8 g. of the title product. M.p. 232-3C.

EXAMPLE 3 l,9-Dimethyl-3,4-dihydro-pyrido[ 2,3-b ]indole-2( lH)-one Five grams of the compound of example 1 are dissolved in 50 ml. of dimethylformamide, then under stirring at l0-20C l.2 g. of 50% sodium hydride (mineral oil emulsion) are added. After standing for 2 hours at 20C, 1.75 ml. of methyl iodide are added. The mixture is stirred for 3 hours at 22C and then poured into ice water (250 ml.). The solid precipitated is crystallized from acetone/hexane. Yield 4 g. of the title product. M.p. 1279C.

EXAMPLE 4 9-Benzyll -methyl-3 ,4-dihydro-pyrido [2,3-b]indole-2( l H )-one The title compound is obtained by following the same procedure as in example 3 by using as the starting compounds 9-benzyl-3,4-dihydro-pyrido[ 2,3-b ]indole- 2( lH)-one and methyl iodide. The title product melts at l8920lC.

EXAMPLE 5 a. lBenzyl-9-methyl-3,4-dihydro-pyrido[ 2,3-b ]indole -2(lH)-one b. 4a-Benzyl-9-methyl-4,4a-dihydro-pyrido [2,3-b] indole-2(3H)-one A mixture of the two title compounds is obtained by reacting 8 g. of 9-methyl-3,4-dihydro-pyrido[ 2,3-b ]indole-2( ll-l)-one with 4.8 ml. of benzyl bromide according to the procedure described in example 3. The mixture is dissolved in ethyl acetate and the solution extracted several times with diluted HCl. The organic phase, after washing subsequently with aqueous sodium bicarbonate and water is evaporated giving an oily residue which is taken up with hexane and then is crystallized from methanol. Yield 1.8 g. of l-benzyl-9- methyl-3,4-dihydro-pyrido[2,3-b] indole-2( lH )-one. M.p. l05-7C. The acidic extracts are combined and after neutralization with l0% sodium hydroxide the mixture is extracted with chloroform. The organic solution is then evaporated and the solid residue is crystallized from ethyl acetate giving 6.5 g. of 4a-benzyl-9- methyl-4,4a-dihydro-pyrido[2,3-b] indole-2(3H)-one. M.p. l-3C.

EXAMPLE 6 l-Acetyl-9-methyl-3,4 -dihydro-pyrido [2,3-b]indole-2( l H)-one Three grams of 9-methyl-3,4-dihydro-pyrido[ 2,3-b indole-2( lH)-one are dissolved in 15 ml. of pyridine an then l0 ml. of acetic anhydride are added. The mixture is heated on a steam bath for 5 hours and then poured into ice water. The solid which precipitates is crystallized from methanol. Yield 2 g. of the title product. M.p. l30-2C.

We claim:

1. A compound of the formula wherein the dotted lines represent an additional bond localized in one of the two possible positions;

R represents lower alkyl of l to 4 carbon atoms and benzyl;

R, represents hydrogen, lower alkyl of l to 4 carbon atoms, benzyl and lower aliphatic acyl of l to 4 carbon atoms and it is present only if the symbol R is absent and the double bond is located between the carbon atoms in position 2 and 3 of the indole ring.

R represents hydrogen, lower alkyl of l to 4 carbon atoms and benzyl and it is present only if the symbol R, is absent and the double bond is located between the positions 1 and 2 of the pyridine ring.

2. 9-Methyl-3,4-dihydro-pyrido[2,3-b]indole2(1H)- one 3. l,9-Dimethyl-3,4-dihydro-pyrido[2,3-b]indole- 2( l H)-one 4. A process for preparing a compound of the formula l wherein the dotted lines represent an additional bond localized in one of the two possible positions;

R represents lower alkyl of l to 4 carbon atoms and benzyl;

R, represents hydrogen, lower alkyl of l to 4 carbon atoms, benzyl and lower aliphatic acyl of l to 4 carbon atoms and it is present only if the symbol R is absent and the double bond is located between the carbon atoms in position 2 and 3 of the indole ring;

wherein the dotted lines represent a double bond localized in one of the two possible positions;

R has the same meaning as before;

R, has the same meaning outlined above and it is present only if the symbol R, is absent and the double bond is located between the carbon atoms in position 2 and 3 of the indole ring;

R, has the same meaning as before and it is present only if the symbol R, is absent and the double bond is located between the iminic substituent and the carbon atom in the position 2 of the indole ring;

R represents hydrogen and lower alkyl of l to 4 carbon atoms, in an organic polar solvent in the presence of a basic agent and, optionally, when in the obtained compound of formula (I) either R, or R represents hydrogen, substituting hydrogen with lower alkyl of l to 4 carbon atoms, benzyl and lower aliphatic acyl of l to 4 carbon atoms by reaction with an agent selected from lower alkyl halogenides, benzyl halogenides in the presence of sodium hydride and lower aliphatic acyl halogenides or anhydrides in the presence of pyridine.

5. A process according to claim 4 for preparing 9- methyl-3 ,4-dihydro-pyrido[2,3-b]indole-2( l H )-one.

6. A process according to claim 4 for preparing l,9-

dimethyl-3,4-dihydro-pyridol2,3-b]indole-2( l H )-one. 

1. THE COMPOUND OF THE FORMULA
 2. 9-Methyl-3,4-dihydro-pyrido(2,3-b)indole2(1H)-one.
 3. 1,9-Dimethyl-3,4-dihydro-pyrido(2,3-b)indole-2(1H)-one
 4. A process for preparing a compound of the formula I
 5. A process according to claim 4 for preparing 9-methyl-3,4-dihydro-pyrido(2,3-b)indole-2(1H)-one.
 6. A process according to claim 4 for preparing 1,9-dimethyl-3, 4-dihydro-pyrido(2,3-b)indole-2(1H)-one. 